Combination cylinder with pawl-actuated emergency release device for the parking brake

ABSTRACT

The invention relates to a combination cylinder including a service brake cylinder as an active service brake with at least one pressure-medium-actuated service brake piston which actuates a brake mechanism via a service brake piston rod, and a spring store brake cylinder as a passive parking brake with a spring store brake piston which is actuated by pressure medium counter to the action of at least one store spring, with the spring store brake piston transmitting the force of the at least one store spring to the service brake piston rod by a force-transmitting gearing in the parking braking situation. The invention provides for the gearing to be designed such that the movements of the spring store brake piston and of the service brake piston rod are coaxial and the force transmission ratio becomes greater with progressive stroke of the spring store brake piston.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of priority to U.S. patentapplication Ser. No. 12/745,988 filed 3 Jun. 2010, which claims thebenefit of priority to International Patent Application No.PCT/EP2008/010052 filed 27 Nov. 2008, and which further claims thebenefit of priority to German Patent Application No. 10 2007 058 670.3filed 6 Dec. 2007, the contents of which are incorporated herein byreference in their entirety.

DESCRIPTION Prior Art

The present invention relates to a combination cylinder comprising aservice brake cylinder as an active service brake with at least onepressure-medium-actuated service brake piston which actuates a brakemechanism via a service brake piston rod, and a spring store brakecylinder as a passive parking brake with a spring store brake pistonwhich may be actuated by pressure medium counter to the action of atleast one store spring, with the spring store brake piston transmittingthe force of the at least one store spring to the service brake pistonrod in the parking braking situation, as per the preamble of claim 1.

In present-day rail vehicles, the spatial conditions in the bogies maybe very restricted. In bogies of high-speed trains in particular, it maybe necessary for up to four brake disks to be arranged on one axle.Furthermore, the installation space for the brakes may be oftenrestricted by drive units or gauge tie bars of electromagnetic railbrakes. These problems may be particularly pronounced if so-calledcombination cylinders, in which a pressure-medium-actuated service brakecylinder as a service brake and a spring store brake cylinder as apassive parking brake may be flange-mounted on one another, may be usedas bogie brakes, because such combination cylinders take up a relativelylarge amount of installation space and may be larger than a servicebrake cylinder without a spring store brake cylinder.

An active brake may be generally understood to mean a brake which may beapplied when pressurized and which may be released in the event of apressure reduction. In most cases, this may be the service brake. Incontrast, in a passive brake such as a spring store brake as a parkingbrake, the brake force may be generated by the store spring, wherein ifthe spring store brake cylinder may be pressurized, said spring storebrake cylinder may be forced counter to the action of the store springinto the brake released position, and said spring store brake cylindermay be moved into the applied position by the action of the store springin the event of a pressure reduction.

To prevent parked rail vehicles from rolling away, the parking brakemust ensure a correspondingly high braking force even without anexternal energy supply. For this purpose, use may be made of springstore brake cylinders with store springs, which impart the braking forcerequired for the parking brake by means of the spring force of the storesprings. The store springs may be preloaded by aerating a spring storebrake chamber. If the spring store brake chamber may be deaerated, thenthe spring force of the store springs may be supported on the levers ofthe brake caliper, and thereby generates the pressure force on the brakelinings.

If a rail vehicle which may be parking-braked in this way must be towed,a compressed air supply for the rail vehicle, by means of which theparking brake designed as a spring store brake can be pneumaticallyreleased, may be often not available. For this situation, the parkingbrake must be equipped with a mechanical emergency release or auxiliaryrelease device, by means of which the parking brake can be released byhand, that is to say without using external energy. In practice, theemergency release device may be also used to set the brake caliper intoa force-free state during brake lining changes, since changing the brakelinings with the parking brake released only pneumatically may be toounsafe, because an undesired application of the spring store brake as aresult of a pressure drop poses too great a safety risk for theservicing personnel.

The emergency release device should also be designed such that, after amechanical release of the spring store brake, the full braking functionmay be available again once the spring store brake chamber has beencharged with a minimum release pressure (automatic return to readiness).

EP 0 072 404 B1 discloses a spring store brake cylinder in which twosprings nested one inside the other act on a coaxial spring store brakepiston. Situated in the piston tube may be a nut thread which may be inengagement with a spindle thread of the piston rod. The threaded spindledrive may be non-self-locking. If the spring store cylinder may bedeaerated, then the springs press via the pistons and piston rods on thepistons of the service cylinder. If an axial force may be transmittedvia the thread, then a torque may be generated between the nut thread inthe piston and the spindle thread, which torque must be supported. Forthis purpose, a coupling sleeve may be arranged in a movable butrotationally fixed manner (for example by a splined shaft profile) onthe spindle, which coupling sleeve may be coupled in a rotationallyfixed manner in the direction of the thread torque by a wrap spring to atube piece fixedly screwed to the piston. For an emergency release, thehook-shaped end of the wrap spring may be rotated by means of theslotted coupling sleeve in the direction in which the coils may beexpanded. Here, the spindle may be screwed in the piston and therebyrotates the coupling sleeve, such that the wrap spring may be contractedagain from the other side. For the complete dissipation of the brakeforce, the coupling sleeve must be rotated to a correspondingly greatextent.

A disadvantage of said type of emergency release may be that its actionmay be slow and it requires a very long actuating travel. A remoteactuation, in order to operate the emergency release device for examplefrom the side of the vehicle, can therefore be realized only with agreat deal of difficulty.

EP 0944512 B1 discloses a generic combination cylinder having a springstore brake cylinder in which a plurality of springs may be arranged ina stellate fashion and interact with two spring store brake pistonswhich may be arranged in series. The piston tube of one of the twospring store brake pistons may be provided with a nut thread whichengages into the thread of a tubular spindle. If the two spring storebrake cylinders may be deaerated, then the spring force may be supportedvia the thread of the one spring store brake piston on the spindle. Thelatter in turn transmits the force via its end side into the piston tubeof the service brake piston, and to the adjusting mechanism accommodatedtherein, and from there to the brake caliper.

The thread torque generated by the spring force may be supported firstlyby the spring store brake piston with the nut thread via two guide boltsin the intermediate base of the spring store brake cylinder. Secondly,the torque acting on the spindle may be supported by a bar in thecylinder housing, which bar engages into a longitudinal groove in thespindle tube and may be guided in a bore in the cylinder housing. Duringthe braking stroke, the bar slides in the groove of the spindle underincreasing torque. If, for the emergency release of the spring store,the bar may be pulled out of the groove of the spindle and therefore thesupport of the spindle torque may be eliminated, then the spindle turnsto the right in the spring store brake piston until it abuts against theintermediate base and the spring store brake piston abuts against thecylinder base. Here, the service brake piston passes into the releaseposition, and the brake may be free from force.

A disadvantage of said arrangement of the torque support may be that, atall braking strokes of the spring store, a sliding movement between thebar and spindle groove takes place under force, and therefore a certainamount of wear occurs on the contact surfaces.

It may be therefore an object of the present invention to furtherdevelop a combination cylinder of the type mentioned in the introductionsuch that it has a lower level of wear.

DISCLOSURE OF THE INVENTION

The invention proposes that the parking brake force generated by thespring store brake piston be introduced into a rotationally fixedlymounted thrust ring which can be actuated coaxially with respect to acentral axis of the combination cylinder and which exerts axial forceson a spindle drive, and an axial force transmission be provided betweenthe spindle drive and the service brake piston rod, with one part of thespindle drive being mounted in a rotationally fixed manner and anotherpart of the spindle drive being rotatably mounted coaxially with respectto a central axis of the combination cylinder, and it being possible forthe rotational movement of the rotatable part of the spindle drive to beblocked by a releasable rotational lock for axial force transmissionbetween the rotationally fixed part and the rotatable part and to beunblocked in order to eliminate said axial force transmission, and withthe rotational lock comprising a manually actuable pawl which can engageinto an external toothing of the rotatable part of the spindle drive andwhich may be rotatably mounted on the thrust ring, and the releasablerotational lock being part of an emergency release device for theemergency release of the parking brake, and the releasable rotationallock being blocked in normal operation and being released for theemergency release of the parking brake.

‘Emergency release’ may be to be understood to mean a mechanical releaseof the spring store brake when the compressed air supply may bedisrupted and consequently the spring store brake piston can no longerbe moved into the released position by pressure medium actuation.

If, for the emergency release of the parking brake, the rotational lockmay be actuated in such a way that the rotatable part of the spindledrive can rotate freely relative to the rotationally fixed part via anon-self-locking gearing, then the rotatable part may be screwed inrelation to the rotationally fixed part of the spindle drive until bothparts may be free from force in relation to one another. Here, thespring store brake piston moves as far as the stop against the base ofthe spring store brake cylinder.

In this way, the torque generated by the force of the store springs ofthe spring store brake may be supported on a very short path between therotatable part and the rotationally fixed part of the spindle drive. Ifthe parking brake is applied, the spring store brake piston, the spindledrive, the thrust ring and the pawl thus perform the braking stroketogether, without a torque having to be supported. In particular, theremay be no sliding surfaces at risk of wear.

Advantageous refinements and improvements of the invention specified inthe independent claims may be possible by means of the measuresspecified in the subclaims.

The pawl may be designed to be pivotable about an axis parallel to thecentral axis of the combination cylinder, and if said pawl can be liftedout of the external toothing of the rotatable part of the spindle driveby pressing a pressure pin which may be movably mounted in thecombination cylinder.

For the emergency release of the parking brake, the rotational lock maybe then released, with the rotatable part of the spindle drive beingscrewed relative to the rotationally fixed part of the spindle drive bymeans of the thread, and with the spring store brake piston moving untilit abuts against a base of the spring store brake cylinder, and with theservice brake piston, driven by a restoring spring, moving together withthe rotatable part of the spindle drive into a released position.

During the emergency release of the parking brake, the pawl can be heldin the lifted-out position via the engagement of a locking pin. As inthe prior art, the spring store brake piston can be forced into therelease position by the pressurization of a spring store brake chamber.Here, according to one refinement of the invention, the thrust ring maybe driven along and the locking pin lifted out, as a result of which thepawl engages into the external toothing of the rotatable part of thespindle drive again, and the rotational lock thereby locks again. Theemergency release device may be thus designed such that, after theemergency release of the spring store or parking brake, the full brakingfunction may be available again once the spring store brake chamber hasbeen charged with a minimum release pressure.

According to one variant, the thrust ring transmits the axial force viaan axial thrust bearing to a gearwheel which forms the rotatable part ofthe spindle drive, into the teeth of which gearwheel can engage the pawlof the rotational lock, with the gearwheel being rotatably mounted on arotationally fixed part of the spindle drive via the thread, whichtransmits the axial force to the service brake piston rod.

Alternatively, the thrust ring and the rotationally fixed part of thespindle drive may be combined and the rotational lock may be arrangedbetween the thrust ring and the rotatable part of the spindle drive.

The parking brake force generated by the spring store brake piston canbe introduced into the thrust ring via a force-transmitting gearing.

In one refinement, two gearings, which may be eccentric in relation tothe central axis, may be provided on the thrust ring such that torquesabout an axis perpendicular to the central axis may be compensated.

In particular, the force-transmitting gearbox may be designed such thatthe movements of the spring store brake piston and of the service brakepiston rod may be coaxial and, in order to realize an approximatelyconstant store spring force on the service brake piston rod over theentire stroke of the spring store brake piston, the force transmissionratio becomes greater with progressive stroke of the spring store brakepiston.

On account of the first measure, the vertical extent of the combinationcylinder may be decreased because the service brake cylinder and thespring brake cylinder can be flange-mounted coaxially on one another.This may be expedient in particular because the vertical installationspace in bogies may be severely restricted and more space may beavailable in the horizontal direction.

The second measure results in an increase in force with progressivestroke of the spring store brake piston, which leads to anadvantageously high parking brake force in the end position of thespring store brake piston, and therefore in the applied state of thespring store brake. The spring store force, which itself falls with thestroke of the spring store piston, may be then compensated by theincreasing force transmission ratio of the gearing. With suitable designof the gearing, it may be possible to realize an approximately constantand high store spring force on the service piston rod over the entirestore of the spring store piston.

According to a refinement, at least one bearing journal which may bearranged perpendicular to the central axis of the combination cylindermay be formed on the thrust ring, on which bearing journal may bepivotably mounted at least one angle lever which may be articulatedlyconnected with its one lever arm to the spring store brake piston andwith its other lever arm to a fixed support surface of the combinationcylinder in such a way that, during an actuation of the spring storebrake piston in the parking braking situation, a rotation of thesupported angle lever about the bearing journal and therefore anactuation of the thrust ring in the same direction may be triggered. Anangle lever of said type then forms an angle gearing, with therespective transmission ratio being determined by the present positionof the angle lever or lever arms of the angle lever.

The parking brake force generated by the spring store brake piston inthe parking brake situation may be consequently introduced via the anglelever as a gearing into the thrust ring, and may be thereby boosted.Said boosted force may be introduced by the thrust ring via theblockable thread into the spindle drive, and may be introduced fromthere via the thrust bearing into the service brake piston tube andfinally into a spindle yoke, the stroke of which ultimately introducessaid boosted force into a brake mechanism, e.g., into a brake caliper ofa disk brake of a rail vehicle.

If two angle levers may be now provided which may be rotatably mountedon bearing journals, which extend outward perpendicular to the centralaxis of the combination cylinder, of the thrust ring, which angle leversmay be arranged reversed in relation to one another with respect to aplane comprising the central axis of the combination cylinder (that isto say the position of one angle lever may be defined by a rotation ofthe other angle lever by 180 degrees about the central axis,point-symmetrical arrangement), then the reaction moments arising fromthe spacing, which acts as a lever, of the angle levers from the centralaxis may be cancelled out, such that advantageously no torque acts onthe thrust ring or on the spring store brake pistons about an axisperpendicular to the central axis (tilting moment).

In each case one lever arm of an angle lever may be connected to thespring store brake piston via a doubly articulatedly connected tensionlug, and in each case one other lever arm of an angle lever may besupported by a support roller which can roll on a fixed support surface,as a result of which wear may be minimized.

To guide the thrust ring in the combination cylinder in a definedrotationally fixed but axially movable manner, the bearing journals ofthe thrust ring bear sliding bodies on the end side, which slidingbodies may be guided in a rotationally fixed manner in sliding-blockguides which extend in the direction of the central axis of thecombination cylinder.

The support surface for the rollable support rollers of the other armsof the angle lever may be formed on a partition between the spring storebrake cylinder and the service brake cylinder, which partition may bepresent in any case, such that no further components may be required.This may be because the partition simultaneously forms a support surfacefor the at least one spring store of the spring store brake cylinder.

According to a further variant of the combination cylinder according tothe invention, by means of the spring store brake piston, at least onewedge contour can be actuated parallel to the central axis of thecombination cylinder, along which wedge contour can be guided a leverarm of at least one lever which may be rotatably mounted on thecombination cylinder and whose other lever arm may be supported on thethrust ring, with a guidance of the one lever arm of the lever along thewedge contour causing a rotational movement of the lever about a leverrotational axis and therefore an axial force, in the same direction asthe movement of the spring brake cylinder, on the thrust ring. Here, thelever rotational axis of the lever may be for example arrangedperpendicular to the central axis of the combination cylinder.

In one refinement of the measure, two wedge contours may be providedwhich engage at least partially around the thrust ring as viewed in thedirection of the lever rotational axis of the lever, which wedgecontours interact with two levers which may be symmetrical with respectto the central axis of the combination cylinder and may be combined toform a double lever. The two levers result in an improved loaddistribution. Furthermore, the load distribution may be symmetrical.

Consequently, if the spring store brake cylinder, in the parking brakesituation, moves in the application direction, then the two wedgecontours may be moved concomitantly, as a result of which the one leverarms of the rotational levers may be moved along the wedge contours andthereby trigger a rotational movement of the rotational levers, as aresult of which the other lever arms of the rotational levers set thethrust ring in an axial movement in the same direction as the movementof the spring store brake piston. The thrust ring, which may berotationally fixedly mounted in the combination cylinder, then transmitsthe axial force acting thereon via the axial thrust bearing to therotating part of the spindle drive, which however in normal operationmay be prevented from rotating relative to the rotationally fixed partof the spindle drive by the rotational locking device. The axial forcemay be then transmitted by the rotationally fixed part to the servicebrake piston rod.

According to a further variant of the combination cylinder according tothe invention, a sliding-block guide mechanism as a gearing comprisingat least one roller lug, which may be articulatedly connected to thethrust ring, may be provided with at least one sliding-block guide inwhich may be guided at least one sliding-block guide lever which may bearticulatedly connected at one side to the housing of the combinationcylinder and at the other side to at least one tension lug which may bearticulatedly connected to the spring brake cylinder.

Here, the roller lug may be provided, on its end pointing away from thethrust ring, with a rotatable roller which can roll on a sliding-blockguide surface of the sliding-block guide lever. The thrust ring may befor example mounted in a non-rotatable manner in the housing of thecombination cylinder by at least one sliding guide.

If two roller lugs with sliding-block guides, two sliding-block guidelevers which may be guided in the sliding-block guides, and two tensionlugs may be provided, which may be arranged reversed in relation to oneanother with respect to a plane comprising the central axis of thecombination cylinder, then tilting moments arising from an actuation ofthe gearing may be compensated.

Consequently, if the spring store brake piston moves in the applicationdirection in the parking brake situation, then the spring force of thestore spring may be supported on the thrust ring via the two tensionlugs, the sliding-block guide lever and the roller lugs. The thrust ringthen dissipates the force to the service brake piston rod and thereforeto the brake mechanism. On account of this kinematic arrangement, ineach case one roller lug may be automatically set to the angularposition, which may be dependent on the stroke of the spring store brakepiston, of the associated sliding-block guide lever, because the rollerlug assumes the position in which the line of force action of the rollerlug may be perpendicular to the tangent of the sliding-block guidesurface at the contact point of the support roller. As a result of thekinematically induced adaptation of the position of the roller lugs as afunction of the stroke of the spring store brake piston, thetransmission ratio of the gearing formed in this way may be increased.

As in the other exemplary embodiments, it may be possible by means ofthese kinematics of the gearing, too, for the spring store brakecylinder and the service brake cylinder to be arranged coaxially withrespect to the central axis of the combination cylinder, with themovements of the service brake cylinder and of the spring store brakecylinder being in the same direction during brake application andrelease situations.

Not least, the invention also relates to a brake caliper unit of a diskbrake of a rail vehicle comprising one of the above-describedcombination cylinders.

Greater detail will be entered into in the following description ofexemplary embodiments of the invention.

FIGURES

Exemplary embodiments of the invention may be illustrated in the drawingand may be explained in more detail in the following description, inwhich:

FIG. 1 shows a plan view of a brake caliper unit of a rail vehiclehaving a combination cylinder according to the invention;

FIG. 2 shows a vertical cross longitudinal cross-sectional illustrationof the combination cylinder from FIG. 1 with a combination cylinderaccording to a first embodiment in the released position;

FIG. 3 shows a cut-away perspective illustration of the combinationcylinder from FIG. 2;

FIG. 4 shows a longitudinal cross-sectional illustration of thecombination cylinder from FIG. 2 with the combination cylinder in theapplied position;

FIG. 5 shows a central vertical longitudinal cross-sectionalillustration of the combination cylinder from FIG. 2 in the releasedposition;

FIG. 6 shows a diagram illustrating the dependency of the spring force,the transmission ratio i of a gearing of the combination cylinder andthe cylinder force on the stroke s of a spring store piston of thecombination cylinder according to the invention;

FIG. 7 shows a horizontal central longitudinal cross section of acombination cylinder according to a further embodiment in the releasedposition;

FIG. 8 shows a cut-away perspective illustration of the combinationcylinder from FIG. 7;

FIG. 9 shows a horizontal longitudinal cross section of the combinationcylinder from FIG. 7 in the braking position;

FIG. 10 shows a vertical central longitudinal cross section of thecombination cylinder from FIG. 7;

FIG. 11 shows a cross-sectional illustration of the combination cylinderfrom FIG. 7;

FIG. 12 shows a vertical longitudinal cross-sectional illustration of acombination cylinder according to a further embodiment in the releasedposition;

FIG. 13 shows a cut-away perspective illustration of the combinationcylinder from FIG. 12;

FIG. 14 shows a vertical longitudinal cross section of the combinationcylinder from FIG. 12 in the braking position;

FIG. 15 shows a horizontal central longitudinal cross section of thecombination cylinder from FIG. 12 in the released position.

DESCRIPTION OF THE EMBODIMENTS

The brake caliper 1 of a rail vehicle shown in FIG. 1 has two brakecaliper levers 2, 4 which run substantially parallel to one another. Thetwo brake caliper levers 2, 4 may be articulatedly connected to oneanother in the central region of their longitudinal extent by a tensionrod 6. The brake caliper levers 2, 4 and the tension rod 6 lie in or runparallel to a brake caliper plane which runs parallel to the drawingplane.

The one ends of the brake caliper levers 2, 4 bear brake pads 8 whichmay be articulatedly connected by means of bolts and which can engage ina frictionally locking manner into a brake disk 10. Situated between theother ends of the brake caliper levers 2, 4 is a combination cylinder12, whose housing 14 may be articulatedly connected to one brake caliperlever 4 and whose service brake piston may be articulatedly connectedvia a service brake piston rod and a spindle yoke 16 to the other brakecaliper lever 2.

It can be seen on the basis of FIG. 1 that the brake caliper 1 has onlya small transmission ratio corresponding to the lever ratios of thebrake caliper levers 2, 4, that is to say the pressure force of thebrake pads 8 may be higher by only a small transmission ratio factorthan the spreading force, which can be exerted by the combinationcylinder 12, for the brake caliper levers 2, 4.

FIG. 2 therefore illustrates in the released position a combinationcylinder 12 with which a higher brake force can be obtained in theparking brake situation. The combination cylinder 12 comprises a servicebrake cylinder 18 as an active service brake with apressure-medium-actuated service brake piston 20 which actuates thebrake caliper lever 2 via a service brake piston rod 22 and via thespindle yoke 16, with the pressurization of and release of pressure fromthe service brake piston 20 taking place by respective aeration anddeaeration of a service brake chamber 24. An anti-twist facility, forexample by a bolt 26 which may be held in the combination cylinder 12and which may be guided axially in the service brake piston 20, ensuresthat the service brake piston 20 may be rotationally fixedly guided inthe service brake cylinder 18. A restoring spring 28 pre-loads theservice brake piston 20 into the right-hand-side released position shownin FIG. 2.

The service brake cylinder 18 may be flange-mounted, coaxially withrespect to a central axis 32 of the combination cylinder 12, on a springstore brake cylinder 30 as a passive parking brake, in which springstore brake cylinder 30 may be guided a spring store brake piston 36which can be actuated by pressure medium counter to the action of, e.g.,a plurality of store springs 34 arranged one inside the other. The storesprings 34 may be accommodated in a spring chamber 38 of the springstore brake cylinder 30, and here may be supported at one side on thespring store brake piston 36 and at the other side on a partition 40between the spring store brake cylinder 30 and the service brakecylinder 18. By pressurizing a spring store brake chamber 42 formed onthe other side of the spring store brake piston 36, the spring storebrake piston 36 moves counter to the action of the store springs 34 intothe right-hand-side released position shown in FIG. 2.

In the parking brake situation, the spring store brake piston 36transmits the force of the store springs 34 via a force-transmittinggearing 44 to the service brake piston rod 22 and to the service brakepiston 20 which may be attached thereto. The force may be thentransmitted from the service brake piston rod 22 to the spindle yoke 16and from there to the corresponding brake caliper lever 2 in order tobring about an application movement of the brake caliper 1, during whichthe brake pads 8 come into frictionally locking engagement with thebrake disk 10.

Here, the gearing 44 may be designed such that the movements of thespring store brake piston 36 and of the service brake piston 20 may becoaxial and the force transmission ratio i of the gearing 44 becomesgreater with progressive stroke s of the spring store brake piston 36,as shown in particular by the curve in FIG. 6.

As can be seen from FIG. 5, a spindle 46 projects through a passageopening of the partition 40 in the direction of the service brake piston20, from which the service brake piston rod 22 in the form of a servicebrake piston tube extends into the interior of the spindle 46 in such away that the spindle 46 may be rotatably mounted on the service brakepiston tube 22, for example by a plain bearing arrangement. Axial thrustbearings 48 may be arranged on radially outer shoulders of the servicebrake piston tube 22, by means of which axial thrust bearings 48 athrust force can be transmitted from the spindle 46 to the service brakepiston tube 22. Therefore, the spindle 46 and the service brake pistontube 22, and the spring store brake piston 36 and the service brakepiston 20, may be arranged coaxially with respect to one another and inparticular with respect to a central axis 32 of the combination cylinder12.

To realize the force transmission by means of the gearing 44, as shownin an embodiment of the combination cylinder 12 in FIG. 2, at least oneangle lever 54 may be mounted, so as to be pivotable about an axisperpendicular to the central axis 32 of the combination cylinder 12, ona thrust ring 50 in which the spindle 46, which may be rotatably mountedon the service brake piston tube 22, can be screwed by anon-self-locking thread 52 (see FIG. 5), which angle lever 54 may bearticulatedly connected with its one end to the spring store brakepiston 36 and with its other end to a fixed support surface 56 of thecombination cylinder 12 (FIG. 2).

Two angle levers 54 may be provided which may be rotatably mounted onbearing journals 58, which extend outward perpendicular to the centralaxis 32 of the combination cylinder 12, of the thrust ring 50, whichangle levers 54 may be arranged reversed in relation to one another withrespect to a plane comprising the central axis 32 of the combinationcylinder, that may be to say the ends of the angle lever 54 may bearranged so as to run oppositely, as can be seen best from FIG. 3.

FIG. 2 shows that, e.g., in each case the one end of a lever arm 60 ofan angle lever 54 may be connected to the spring store brake piston 36by a doubly articulatedly connected tension lug 64, and the other end ofthe other lever arm 62 of an angle lever 54 may be supported by asupport roller 66 which can roll on the fixed support surface 56 andwhich may be rotatably mounted on the other lever arm 62 of the anglelever 54. The support surfaces 56 for the rollable support rollers 66 ofthe angle levers 54 may be formed on the partition 40 between the springstore brake cylinder 30 and the service brake cylinder 18 and facetoward the spring chamber 38 in which the store springs 34 may beaccommodated.

To guide the thrust ring 50 in the combination cylinder 12 in arotationally fixed but axially movable manner, the bearing journals 58of the thrust ring 50 bear sliding bodies 68 on the end side, whichsliding bodies may be guided in sliding-block guides 70 (FIG. 3) whichextend in the direction of the central axis 32 of the combinationcylinder 12 and which may be formed in the spring store brake piston 36.The spring store brake piston 36 in turn may be prevented from twistingin the spring brake cylinder 30 by at least one guide bolt 72 whichextends parallel to the central axis 32 of the combination cylinder 12and may be fixedly connected to the spring store brake piston 36 and maybe guided in the partition 40, such that the thrust ring 50 may be alsosupported in a rotationally fixed manner in the spring brake cylinder30.

The spindle 46 can be screwed relative to the thrust ring 50, moreprecisely in the thrust ring 50, by means of the non-self-locking thread52 (FIG. 5) which can be blocked and unblocked by a releasablerotational lock 74. The releasable rotational lock 74 may be part of anemergency release device 76 for the emergency release of the springstore brake cylinder 30. ‘Emergency release’ is to be understood to meana mechanical release of the spring store brake when the compressed airsupply may be disrupted and consequently the spring store brake piston36 can no longer be moved into the released position by pressure mediumactuation.

The angle lever 54 then forms an angle gearing 44, with the respectivetransmission ratio i being determined by the present position of theangle lever 54 or lever arms 60, 62 of the angle lever 54. Therefore, inthe parking brake situation in which the spring store brake chamber 42may be deaerated and therefore the spring store brake piston 36 may beforced by the action of the store springs 34 from the released positionshown in FIG. 2 into the applied position shown in FIG. 4, force may beintroduced from the spring store brake piston 36 into the tension lugs64, which may be articulatedly connected thereto and which in turn maybe articulatedly connected to the one lever arm 60 of an angle lever 54,and via the two angle levers 54 into the thrust ring 50, with the anglelevers 54 thereby being firstly pulled along and secondly rotated, withthe angle levers 54 supporting the reaction forces on the fixed supportsurface 56. Depending on the rotational position of the angle levers 54,the lever arms 60, 62 of the angle levers 54 have a different effectivelever length a and b in relation to the central axes of the bearingjournals 58 of the thrust ring 50, as shown by a comparison of FIG. 2(released position) with FIG. 4 (applied position).

In other words, the lever lengths a and b, which act for generating thetorque, on the lever arms 60, 62 of the angle lever 54 vary as afunction of the respective rotational position of the angle lever 54,which in turn may be dependent on the stroke of the spring store brakepiston 36. Therefore, however, the transmission ratio i of the levergearing 44 formed by the angle lever 54 varies as a function of thestroke of the spring store brake piston 36 in the present case in such away that the force transmission ratio i increases, that is to say arelatively large travel of the spring store brake piston 36 with arelatively small spring force of the store springs 34 may be transformedinto a small travel of the spindle yoke 16 with a relatively largespreading force for the brake caliper 1. Here, a person skilled in theart will select the geometry, in particular the lengths of the leverarms 60, 62 of the angle levers 54, in such a way that the forcetransmission ratio i on account of the angle lever 54 increases withincreasing rotational angle or with increasing stroke of the springstore brake piston 36, as shown by the curve in FIG. 6.

If, therefore, the spring store brake cylinder 30 may be deaerated inorder to apply the parking brake, then the spring force of the storesprings 34 may be supported via the spring store brake piston 36 and thetension lugs 64 on in each case the one lever arm 60 of the two anglelevers 54. Here, the angle levers 54, which may be rotatably mounted onthe thrust ring 50, may be supported with the support roller 66 of thein each case other lever arm 62 on the support surface 56 of thepartition 40. The sum F_(D) of the spring force F_(Spring) and theroller force F_(R) may be transmitted here in the axial direction to thethrust ring 50, the spindle 46 and the service brake piston tube 22 tothe spindle yoke 16.

With progressive stroke of the spring store brake piston 36 and theassociated rotation of the angle lever 54, the effective transmissionratio i of the angle lever 54 increases. With suitable selection of thelengths of the lever arms 60, 62 and/or of the angle between the leverarms 60, 62 and/or of the lengths of the tension lugs 64 and/or theposition of the articulated connection thereof to the spring store brakepiston 36, the reduction of the spring force of the store springs 34over the stroke of the spring store brake piston 36 may be compensatedby the increasing transmission ratio i, so as to yield approximately aprofile as per FIG. 6 of the brake force acting on the spindle yoke 16,which may be approximately constant over the stroke s of the springstore brake piston 36.

By means of the two tension lugs 64 which engage at an angle on thespring store brake piston 36, a torque about the central axis 32 of thecombination cylinder 12 may be introduced both into the spring storebrake piston 36 and also into the thrust ring 50. The torque may besupported by the sliding bodies 68, which may be guided in thesliding-block guides 70, of the thrust ring 50 in the spring store brakepiston 36, which in turn may be held in a rotationally fixed manner bythe guide bolts 72 in the spring store brake cylinder 30 (FIG. 2).

The parking brake force generated by the spring store brake piston 36may be consequently introduced into the thrust ring 50 via the anglelever 54 as a gearing 44, and may be thereby boosted. The boosted forcemay be introduced from the thrust ring 50 via the blockable thread 52into the spindle 46, and from there via the axial thrust bearing 48 intothe service brake piston tube 22 and the spindle yoke 16, the stroke ofwhich, which may be thereupon directed to the left in FIG. 2 or FIG. 4,ultimately transforms the force into a rotation of the brake caliperlevers 2, 4.

If no compressed air may be available for releasing the parking brake,for example on account of a defect or a leak in the compressed airsystem, then the parking brake can be released by manually actuating theemergency release device 76. For this purpose, by pressing a pressurepin 78 which may be vertically movably mounted in the combinationcylinder 12, a pawl 80 which may be pivotable on the thrust ring 50about an axis parallel to the central axis 32 of the combinationcylinder 12 may be lifted out of an external toothing 82 of the spindle46, as a result of which the rotational lock between the spindle 46 andthe thrust ring 50 may be eliminated (FIG. 3). Since the thread 52between the parts may be not self-locking, the spindle 46 may be screwedin the thrust ring 50 until both parts may be free from axial forces andthe spring store brake piston 36 abuts against the base of the springstore brake cylinder 30. The service brake piston 20 can also, driven bythe restoring spring 28, assume the released position together with thespindle 46.

The pawl 80 may be held in the lifted-out position as a result of theengagement of a locking pin 84 (FIG. 3). Only when the spring storebrake piston 36 may be forced into its released position by thepressurization of the spring store brake chamber 42, and thereby drivesthe thrust ring 50, may be the locking pin 84 lifted out as a result ofcontact against the partition 40, as a result of which the pawl 80 canengage into the external toothing 82 of the spindle 46 again and therebyproduce the rotational lock between the spindle 46 and the thrust ring50 again.

A wear adjuster may be accommodated within the service brake piston tube22, which wear adjuster may be formed for example by a single-actingstep adjuster. During a service braking operation, the service brakechamber 24 may be aerated, as a result of which the service brake piston20 actuates the spindle yoke 16, and therefore the brake caliper 1, viathe service brake piston rod 22.

In the second exemplary embodiment of the invention according to FIGS. 7to 11, those parts which remain the same and have the same action inrelation to the preceding example may be denoted by the same referencesymbols. In contrast to the preceding example, at least one wedgecontour 86 can be actuated parallel to the central axis 32 of thecombination cylinder 12 by the spring store brake piston 36, along whichwedge contour 86 a lever arm 88 of at least one lever 90 which may berotatably mounted on the combination cylinder 12 can be guided, theother lever arm 92 of which lever 90 may be supported on the thrust ring50, with a guidance of the one lever arm 88 of the lever 90 along thewedge contour 86 causing a rotational movement of the lever 90 about alever rotational axis 94 and therefore, by means of the other lever arm92, generating an axial force which acts on the thrust ring and whichmay be aligned in the same direction as the movement of the spring storebrake piston 36, as can be seen best from FIG. 8. Here, for example thelever rotational axle 94 of the lever 90 may be arranged perpendicularto the central axis 32 of the combination cylinder 12 and may be mountedfor example in the cylinder cover 96 of the spring store brake cylinder30.

The two wedge contours may be symmetrical in relation to the centralaxis 32 to be provided on two wedge plates 86, which at least partiallysurround the thrust ring 50 and which interact with two levers 90 whichmay be symmetrical with respect to the central axis 32 of thecombination cylinder 12 and which may be combined in each case to form adouble lever. A double lever 90 of the type consequently comprises anupper lever 90 a and a lower lever 90 b with in each case one lever arm88 guided on the respective wedge contour 86 and with in each case onelever arm 92 guided on a support surface of the thrust ring 50 (FIG. 8).

In the variant, the thrust ring 50 transmits the axial force for examplevia an axial thrust bearing 98 to a rotatable part of a spindle drive inthe form of a gearwheel 100 which can be rotated, on a rotationallyfixed part 102 of the spindle drive, by means of the non-self-lockingthread 52 about an axis which may be coaxial with respect to the centralaxis 32 (FIG. 10). The pawl 80 of the rotational lock 74 of theemergency release device 76 can again engage into the external toothing82 of the gearwheel 100, which pawl 80 may be rotatably mounted in thecylinder cover 96 (FIG. 11). The rotationally fixed part 102 of thespindle drive can then transmit the axial force to the service brakepiston rod 22.

As can be seen in particular from FIG. 11, the pawl 80 may be designedas a tilting lever which may be rotatable about a rotational axis 104parallel to the central axis 32 and which can engage at one end into theexternal toothing 82 of the gearwheel 100 and which can be acted on atthe other end by the spring-preloaded, manually actuable pressure pin 78which projects slightly out of the housing 14 through a passage bore, inorder, as a function of the position of the pressure pin 78, torotationally fixedly connect the gearwheel 100 to the housing 14 of thecombination cylinder 12 or to release the connection in order to allowthe gearwheel 100 to freely rotate on the rotationally fixed part 102 ofthe spindle drive.

Consequently, if the spring store brake cylinder 30 moves from thereleased position shown in FIG. 7 into the applied position shown inFIG. 9 in the parking brake situation, then the two wedge contours 86may be moved concomitantly, as a result of which the one lever arms 88of the double levers 90 may be moved along the wedge contours 86 andthereby trigger a rotational movement of the double lever 90, as aresult of which the other lever arms 92 set the thrust ring 50 in anaxial movement in the same direction as the movement of the spring storebrake piston 36, as can be seen best from FIG. 8. At the end side, theother lever arms 92 of the double lever 90 may be for example providedwith rollers 104 in order to enable rolling on the wedge contours 86 oron the thrust ring 50.

The transmission ratio i may be determined from the lengths a and b ofthe lever arms 88, 92 of the rotary levers 90 and from the wedge anglea, which may be dependent on the stroke of the spring store brakecylinder 30, of the wedge contours 86 at the respective contact point ofthe rollers 104 (cf. FIG. 7 and FIG. 9):

$i = \frac{a}{{b \cdot \sin}\; \alpha}$

The thrust ring 50 which may be rotationally fixedly mounted in thecombination cylinder 12 then transmits the axial force acting thereonvia the axial thrust bearing 98 to the gearwheel 100, which may behowever prevented from rotating relative to the rotationally fixed part102 in normal operation by the rotational lock 74. The axial force maybe then transmitted from the rotationally fixed part 102 of the spindledrive to the service brake piston rod 22.

In normal operation, the pressure pin 78 of the rotational lock 74 maybe loaded in the outward direction by a spring such that the pawl 80engages into the external toothing 82 of the gearwheel 100 and preventsthe latter from rotating (FIG. 11). If, for the emergency release of theparking brake, the pressure pin 78 of the rotational lock 74 may be thenactuated by being pressed, the pawl 80 tilts about the rotational axis,as a result of which it passes out of engagement at one end side withthe external toothing 82 of the gearwheel 100. This has the effect thatthe gearwheel 100 can rotate freely relative to the rotationally fixedpart 102 of the spindle drive by means of the non-self-locking thread 52until both parts may be free from force in relation to one another.Here, the spring store brake piston 36 moves until it abuts against thebase of the spring store brake cylinder 30, and the service brake piston20 can, driven by the restoring spring 28, move together with thespindle 46 into the released position shown in FIG. 7.

In the third exemplary embodiment of the invention according to FIGS. 12to 15, those parts which remain the same and have the same action inrelation to the preceding example may be denoted by the same referencesymbols.

As in the other exemplary embodiments, the spring store brake cylinder30 and the service brake cylinder 18 may be arranged coaxially. As astore spring 34, provision may be made for example of a conical springwhich may be braced by an annular spring store brake piston 36.

Between the spring store brake piston 36 and the service brake pistonrod 22 of the service brake cylinder 18, two sliding-block guidemechanisms 106 may be arranged reversed in relation to one anotherpoint-symmetrically or in relation to a plane comprising the centralaxis 32 of the combination cylinder 12, which sliding-block guidemechanisms 106 transmit the force of the store springs 34 to the servicebrake piston rod 22 of the service brake cylinder 18. A sliding-blockguide mechanism 106 may be composed substantially of a sliding-blockguide lever 108, whose one end may be rotatably mounted on the cylinderhousing 14 and whose other end may be articulatedly connected to thespring store brake piston 36 via a tension lug 110, and of a roller lug112 which may be rotatably mounted at one end on the thrust ring 50 andwhich, at the other end, bears a support roller 114 which may be inengagement with a sliding-block guide surface 116 of the sliding-blockguide lever 108.

If the spring store brake piston 36 performs a stroke, then thesliding-block guide lever 108 rotates about its bearing point on abearing block 118 in the cylinder housing. As a result of the rotationof the sliding-block guide lever 108, the angle between the roller lug112 and the sliding-block guide surface 116 varies, which angle may benormally set to 90 degrees. The roller lug 112 thereupon rotatesautomatically until the line of force action may be again perpendicularto the tangent of the sliding-block guide surface 116 at the contactpoint of the support roller 114. In this way, the effective lever armsand consequently also the transmission ratio may be varied.

By means of suitable selection of the sliding-block guide geometry, theposition of the bearing points and the lever and lug lengths, it may bepossible to obtain a transmission ratio which increases over the pistonstroke of the spring store brake piston 36, by means of which thedecrease in force of the store spring 34 over the stroke may becompensated or at least reduced.

As in the other exemplary embodiments, the cylinder housing 14 of thecombination cylinder 1 may be composed substantially of three partswhich may be screwed to one another. The service brake cylinder 18 maybe situated in the left-hand cylinder half (FIG. 15), the spring storebrake cylinder 30 may be arranged in the right-hand half and may beclosed off by the cylinder cover 96. The assemblability of the springstore brake cylinder 30 may be ensured by means of the cylinder cover96.

The annular service brake piston 20 may be fixedly connected to theservice brake piston tube 22, for example by a pressure-tightinterference fit, and may be sealed off at the outer diameter by apressed-on sleeve and at the inner diameter by a shaft sealing ringbetween the cylinder base and service brake piston tube 22. The servicebrake piston 20 may be prevented from rotating relative to the housingby at least one guide bolt.

The service brake piston tube 22 may be guided firstly in the servicebrake cylinder 18 and secondly in the partition 40. The spring storebrake cylinder 30 also comprises an outer sealing surface for the springstore brake piston 36 which may be designed as an annular piston, andthe spring store brake cylinder 30 has guide surfaces for sliding blocks68 of the thrust ring 50, which in turn may be held on the ends of twobearing journals 58, which project away perpendicularly to the centralaxis 32, of the thrust ring 50 (FIG. 13). Air ports (not visible in thesectional illustrations) may be formed in the partition 40 for thespring store brake chamber 42 and the service brake chamber 24. Thespring store brake piston 36 may be provided with seals on the inner andouter diameter. Screwed, for example, to the spring store brake piston36 may be bearing journals for the tension lugs 110 which may bearticulatedly connected thereto, with the rotational axes thereof beingarranged perpendicular to the central axis 32 of the combinationcylinder 1. The store spring 34, which may be designed here for exampleas a conical spring, may be supported at one side on the cylinderhousing 14 and at the other side on the spring store brake piston 36.

The sliding-block guide levers 108 may be articulatedly connected at oneside via the tension lugs 110 to the spring store brake piston 36, andmay be rotatably mounted at the other side in the bearing blocks 118which may be fixedly screwed to the cylinder housing 14. The roller lugs112 which may be mounted on the bearing journals 58 of the thrust ring50 about an axis perpendicular to the central axis 32 of the combinationcylinder 12 have, at their ends pointing away from the bearing journals58, the support rollers 114 which finally introduce the force from thesliding-block guide levers 108 into the thrust ring 50.

The pawl 80 of the rotational lock 74 of the emergency release device 76may be mounted on the thrust ring 50 (FIG. 13). The emergency releasedevice 76 again comprises a non-self-locking thread 52 for themechanical dissipation of the parking brake force if no compressed airmay be available for bracing the store spring 34, and also comprises thegearwheel 100 which can be screwed by the non-self-locking thread 52 onthe rotationally fixed part 102 of the spindle drive and which may berotatably mounted by means of for example two rolling bearings 120 inthe thrust ring 50, the rotationally fixed part 102 of the spindledrive, which rotationally fixed part engages via two claws into a slotof the service brake piston tube 22 and thereby may be firstlyrotationally fixed with the latter and secondly can transmit axialforces to the service brake piston tube 22 in the brake applicationdirection, and the pawl 80 which may be mounted in the thrust ring 50and which can be placed in engagement with the gearwheel 100. The pawl80 supports the torque generated in the non-self-locking thread 52 andconducts the torque to the thrust ring 50, which in turn may besupported by the sliding blocks 68 in sliding-block guides of thecylinder housing 14. As in the other exemplary embodiments, during anemergency release actuation, the pawl 80 may be lifted manually out ofthe external toothing 82 of the gearwheel 100.

For the pneumatic release of the spring store brake cylinder 30 (FIG.12), the spring store brake chamber 42 may be acted on with pressure,such that the store spring 34 may be preloaded by the spring store brakepiston 36.

To apply the spring store brake (FIG. 14), the spring store brakechamber 42 may be deaerated, such that the spring force of the storespring 34 may be supported via the two tension lugs 110, thesliding-block guide lever 108 and the roller lugs 112 on the thrust ring50. The latter conducts the force via the emergency release device 76 tothe service brake piston tube 22 and from there to the spindle yoke 16.Here, the two roller lugs 112 may be automatically set to the angleposition, which may be dependent on the piston stroke, of thesliding-block guide levers 108. The roller lugs 112 assume the positionin which the line of force action of the roller lugs may beperpendicular to the tangent of the sliding-block guide surfaces 116 atthe respective contact point of the support rollers 114. In other words,the bearing point of the roller lug 112, the central point of thesupport roller 114 and the contact point of the support roller 114 withthe sliding-block guide surface 116 lie on a straight line.

In the embodiment illustrated here, the sliding-block guide surface 116on which the support roller 114 rolls may be planar. Depending on thedesired transmission ratio, however, a concave or convex sliding-blockguide surface 116 may be also conceivable. In the case of a convexsurface, the radius of curvature must be no less than the length of theroller lug 112, in order that a stable equilibrium can be set.

The transmission ratio i, which may be dependent on the stroke of thespring store brake piston 36, can be calculated from the lengths a and bof the effective lever arms and the angles α and β (FIGS. 12 and 14):

$i = \frac{{a \cdot \cos}\; \beta}{{b \cdot \cos}\; \alpha}$

The force F_(St) on the thrust ring 50 or on the spindle yoke 16 may bethen defined as follows:

F _(St) =i·F _(F)

If no compressed air may be available for releasing the applied springstore brake, for example as a result of leakage, then the spring storebrake can be released by manually actuating the emergency release device76. For this purpose, by pressing the emergency release actuating means,the pawl 80 which may be mounted in the thrust ring 50 may be pushed outof the toothing 82 of the gearwheel 100, as a result of which therotational locking between the rotationally fixed part 102 of thespindle drive and the gearwheel 100 may be eliminated. Since the thread52 between the two parts may be not self-locking, the gearwheel 100 maybe screwed on the rotationally fixed part 102 until both parts may befree from force in relation to one another. Here, the spring store brakepiston 36 passes into the released position, and the service brakepiston 20 itself can also, driven by the restoring spring 28, assume therelease position together with the rotationally fixed part 102.

LIST OF REFERENCE SYMBOLS

1 Brake caliper

2 Brake caliper lever

4 Brake caliper lever

6 Tension rod

8 Brake pad

10 Brake disk

12 Combination cylinder

14 Housing

16 Spindle yoke

18 Service brake cylinder

20 Service brake piston

22 Service brake piston rod

24 Service brake chamber

26 Bolt

28 Restoring spring

30 Spring store brake cylinder

32 Central axis

34 Store spring

36 Spring store brake piston

38 Spring chamber

40 Partition

42 Spring store brake chamber

44 Gearing

46 Spindle

48 Axial thrust bearing

50 Thrust ring

52 Thread

54 Angle lever

56 Support surface

58 Bearing journal

60 Lever arm

62 Lever arm

64 Tension lug

66 Support roller

68 Sliding body

70 Sliding-block guides

72 Guide bolt

74 Rotational lock

76 Emergency release device

78 Pressure pin

80 Pawl

82 External toothing

84 Locking pin

86 Wedge contour

88 Lever arm

90 Lever

90 a Upper lever

90 b Lower lever

92 Lever arm

94 Lever rotational axle

96 Cylinder cover

98 Axial thrust bearing

100 Rotatable part of the spindle drive

102 Rotationally fixed part of the spindle drive

104 Rollers

106 Sliding-block guide mechanism

108 Sliding-block guide lever

110 Tension lug

112 Roller lug

114 Support roller

116 Sliding-block guide surface

118 Bearing block

120 Rolling bearing

1. A combination cylinder comprising: a service brake cylinder as anactive service brake with at least one pressure-medium-actuated servicebrake piston that actuates a brake mechanism via a service brake pistonrod; and a spring store brake cylinder as a passive parking brake with aspring store brake piston which is actuated by pressure medium counterto the action of at least one store spring with the spring store brakepiston transmitting the force of the at least one store spring to theservice brake piston rod in the parking braking situation, wherein a)the parking brake force generated by the spring store brake piston isoptionally introduced into a rotationally fixedly mounted thrust ringwhich can be actuated coaxially with respect to a central axis of thecombination cylinder and which exerts axial forces on a spindle drive,and an axial force transmission is provided between the spindle driveand the service brake piston rod, with b) one part of the spindle drivebeing mounted in a rotationally fixed manner and another part of thespindle drive being rotatably mounted coaxially with respect to acentral axis of the combination cylinder, and the rotational movement ofthe rotatable part of the spindle drive is optionally blocked by areleasable rotational lock for axial force transmission between therotationally fixed part and the rotatable part and optionally unblockedto eliminate the axial force transmission, and with c) the rotationallock comprising a pawl which is optionally engage into an externaltoothing of the rotatable part of the spindle drive and which isrotatably mounted on the thrust ring, and the releasable rotational lockbeing part of an emergency release device for the emergency release ofthe parking brake, and d) the releasable rotational lock being blockedin normal operation and being released for the emergency release of theparking brake.
 2. The combination cylinder of claim 1, wherein a threadbetween the rotatable part of the spindle drive and the rotationallyfixed part of the spindle drive is a non-self-locking thread.
 3. Thecombination cylinder of claim 1, wherein the pawl is designed to bepivotable about an axis parallel to the central axis of the combinationcylinder (12), and is optionally lifted out of the external toothing ofthe rotatable part of the spindle drive by pressing a pressure pin whichis movably mounted in the combination cylinder.
 4. The combinationcylinder of claim 1, wherein when the rotational lock is released forthe emergency release of the parking brake, the rotatable part of thespindle drive is screwed relative to the rotationally fixed part of thespindle drive by the thread, with the spring store brake piston movinguntil it abuts against a base of the spring store brake cylinder, andwith the service brake piston, driven by a restoring spring, movingtogether with the rotatable part of the spindle drive into a releasedposition.
 5. The combination cylinder of claim 1, wherein, during theemergency release of the parking brake, the pawl is optionally held inthe lifted-out position by the engagement of a locking pin.
 6. Thecombination cylinder of claim 5, wherein the spring store brake pistonis optionally forced into the release position by the pressurization ofa spring store brake chamber, with the thrust ring being driven alongand the locking pin lifted out, as a result of which the pawl engagesinto the external toothing of the rotatable part of the spindle driveand the rotational lock thereby locks.
 7. The combination cylinder ofclaim 1, wherein the thrust ring transmits the axial force via an axialthrust bearing to a gearwheel which forms the rotatable part of thespindle drive, into the toothing of which gearwheel can engage themanually actuable pawl of the rotational lock, with the gearwheel beingrotatably mounted on a rotationally fixed part of the spindle drive viathe thread, which transmits the axial force to the service brake pistonrod.
 8. The combination cylinder of claim 1, wherein the thrust ring andthe rotationally fixed part of the spindle drive are combined and therotational lock is arranged between the thrust ring and the rotatablepart of the spindle drive.
 9. The combination cylinder of claim 1,wherein the parking brake force generated by the spring store brakepiston is optionally introduced into the thrust ring by aforce-transmitting gearing.
 10. The combination cylinder of claim 9, theforce-transmitting gearing is included in two gearings, which areconcentric in relation to the central axis, are provided on the thrustring such that torques about an axis perpendicular to the central axisare compensated.
 11. The combination cylinder of claim 9, wherein theforce-transmitting gearing is designed such that the movements of thespring store brake piston and of the service brake piston rod arecoaxial and, to realize an approximately constant store spring force onthe service brake piston rod over the entire stroke of the spring storebrake piston, the force transmission ratio becomes greater withprogressive stroke of the spring store brake piston.
 12. The combinationcylinder of claim 11, further comprising at least one bearing journalwhich is arranged perpendicular to the central axis of the combinationcylinder and is formed on the thrust ring, on which bearing journal ispivotably mounted at least one angle lever which is articulatedlyconnected with its one end to the spring store brake piston and with itsother end to a fixed support surface of the combination cylinder in sucha way that, during an actuation of the spring store brake piston in theparking braking situation, a rotation of the supported angle lever aboutthe bearing journal and therefore an actuation of the thrust ring in thesame direction are triggered.
 13. The combination cylinder of claim 12,wherein two angle levers are provided which are rotatably mounted onbearing journals, which extend outward perpendicular to the central axisof the combination cylinder, of the thrust ring, which angle levers arearranged reversed in relation to one another with respect to a planecomprising the central axis of the combination cylinder.
 14. Thecombination cylinder of claim 13, wherein a lever arm of the angle leveris connected to the spring store brake piston via a doubly articulatedlyconnected tension lug.
 15. The combination cylinder of claim 13, whereinanother lever arm of the angle lever is supported by a support rollerwhich is configured to roll on the fixed support surface.
 16. Thecombination cylinder of claim 15, wherein the bearing journals of thethrust ring bear sliding bodies at the end sides, which sliding bodiesare guided in sliding-block guides which extend in the direction of thecentral axis of the combination cylinder.
 17. The combination cylinderof claim 16, wherein the support surface for the angle lever is formedon a partition between the spring store brake cylinder and the servicebrake cylinder.
 18. The combination cylinder of claim 17, wherein thepartition forms a support surface for the at least one store spring ofthe spring store brake cylinder.
 19. The combination cylinder of claim1, wherein the spring store brake piston, at least one wedge contour canbe actuated parallel to the central axis of the combination cylinder,along which wedge contour can be guided a lever arm of at least onelever which is rotatably mounted on the combination cylinder and whoseother lever arm is supported on the thrust ring, with a guidance of theone lever arm of the lever along the wedge contour causing a rotationalmovement of the lever about a lever rotational axis and therefore anaxial force, in the same direction as the movement of the spring brakecylinder, on the thrust ring.
 20. The combination cylinder of claim 19,wherein the lever rotational axis of the lever is arranged perpendicularto the central axis of the combination cylinder.
 21. The combinationcylinder of claim 19, further comprising two wedge contours which engageat least partially around the thrust ring as viewed in the direction ofthe lever rotational axis of the lever, which wedge contours interactingwith two levers including the lever and which are symmetrical withrespect to the central axis of the combination cylinder and are combinedto form a double lever.
 22. The combination cylinder of claim 1, furthercomprising a sliding-block guide mechanism comprising at least oneroller lug, which is articulatedly connected to the thrust ring, and atleast one sliding-block guide in which is guided at least onesliding-block guide lever which is articulatedly connected at one sideto the housing of the combination cylinder and at the other side to atleast one tension lug which is articulatedly connected to the springbrake cylinder.
 23. The combination cylinder of claim 22, wherein the atleast one roller lug is provided, on its end pointing away from thethrust ring, with a rotatable support roller which is configured to rollon a sliding-block guide surface of the sliding-block guide lever. 24.The combination cylinder of claim 22, wherein the thrust ring is mountedin a non-rotatable manner in the housing of the combination cylinder byat least one sliding guide.
 25. The combination cylinder of claim 22,wherein the at least one roller lug is one of two roller lugs withsliding-block guides, the at least one sliding-block guide is one of twosliding-block guide levers which are guided in the sliding-block guides,and the at least one tension lug is one of two tension lugs areprovided, which are arranged reversed in relation to one another withrespect to a plane comprising the central axis of the combinationcylinder.
 26. The combination cylinder of claim 25, wherein the thrustring has two bearing journals which are arranged perpendicular to thecentral axis and which bear in each case one bearing arrangement for aroller lug.
 27. A brake caliper unit of a disk brake of a rail vehiclecomprising at least one combination cylinder as claimed in claim 1.